Shouldn't assignment like
b=. , a
c=. 1{a
just increase reference count of the mother instead of deep copy?On Sun, May 17, 2020, 6:27 AM Henry Rich <[email protected]> wrote: > I wouldn't say so. Reshape takes virtually no time/space, but boxing or > assigning the reshaped result does. If you do something like > > +/ @: (,/) y > > the result of ,/ is never realized and it would be wrong to charge it > with time/space not used. > > Similarly > > (}. - }:) y > > the }. and }: create virtual results that are never realized. > > You need to expand your mental model beyond time/space for a verb, to > include time/space for realization when that becomes necessary. > > Henry Rich > > > On 5/16/2020 1:22 PM, 'Mike Day' via Programming wrote: > > Oh... so one needs to, say, assign the result to see the real t/s? > > > > Thanks, > > > > Mike > > > > Sent from my iPad > > > >> On 16 May 2020, at 17:05, Henry Rich <[email protected]> wrote: > >> > >> The time/space numbers are telling you that (x $ y) produces a virtual > result when it can, while (_2 ]\ y) doesn't (yet). If you use the result > immediately, the space saving is real. If you box the result or save it in > a name, the value will be realized and the space saving will vanish. > >> > >> Henry Rich > >> > >>> On 5/16/2020 11:14 AM, 'Michael Day' via Programming wrote: > >>> Much neater than what I was about to offer, unless Raoul needs to > specify the fill, > >>> > >>> in which case, this alternative rather minimal amendment is worth > consideration: > >>> > >>> ($!._ ~2,~>.@-:@#) i.7 > >>> 0 1 > >>> 2 3 > >>> 4 5 > >>> 6 _ > >>> > >>> cf > >>> > >>> _2]\ i.7 > >>> 0 1 > >>> 2 3 > >>> 4 5 > >>> 6 0 > >>> > >>> Also, the time and space performance _might_ be important for large > inputs: > >>> > >>> ts' $ _2]\ list ' [list =: i.100000 > >>> 0.000618 1.04986e6 > >>> ts'($!._ ~2,~>.@-:@#) list' > >>> 2.7e_6 2304 > >>> > >>> Cheers, > >>> > >>> Mike > >>> > >>>> On 16/05/2020 15:57, 'Rob Hodgkinson' via Programming wrote: > >>>> You could try Infix … here with NuVoc link… > >>>> https://code.jsoftware.com/wiki/Vocabulary/bslash#dyadic > >>>> > >>>> x u\ y where x is eg _2 means apply very b to successive pairs > (_ for non-overlapping). > >>>> > >>>> _2 ]\ 1 2 3 4 5 6 > >>>> 1 2 > >>>> 3 4 > >>>> 5 6 > >>>> _2 ]\ 1 2 3 4 5 6 7 > >>>> 1 2 > >>>> 3 4 > >>>> 5 6 > >>>> 7 0 > >>>> > >>>> _2 <\ 1 2 3 4 5 6 > >>>> ┌───┬───┬───┐ > >>>> │1 2│3 4│5 6│ > >>>> └───┴───┴───┘ > >>>> > >>>> HTH…/Rob > >>>> > >>>>> On 17 May 2020, at 12:42 am, Raoul Schorer <[email protected]> > wrote: > >>>>> > >>>>> Hello, > >>>>> > >>>>> I am convinced that this must be trivial, but I wasn't able to find > in the documentation how to reshape a list to a table without manually > extracting the length. > >>>>> > >>>>> in summary, is there a more direct way of doing: > >>>>> > >>>>> lst =. i. 6 > >>>>> > >>>>> ((2,~2%~#) $ ]) lst > >>>>> > >>>>> for a list of arbitrary length? > >>>>> > >>>>> Thanks! > >>>>> > >>>>> Raoul > >>>>> > >>>>> > ---------------------------------------------------------------------- > >>>>> For information about J forums see > http://www.jsoftware.com/forums.htm > >>>> ---------------------------------------------------------------------- > >>>> For information about J forums see > http://www.jsoftware.com/forums.htm > >>> > >> > >> -- > >> This email has been checked for viruses by AVG. > >> https://www.avg.com > >> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
